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Biomedical subjects

K Muramatsu

Publications and source records attributed to K Muramatsu.

At least 37 records · Page 2Linked to original sources
PubMed2000

Electron spin resonance studies of dipalmitoylphosphatidylcholine liposomes containing soybean-derived sterylglucoside.

The effects of soybean-derived sterylglucoside (SG) on the fluidity of liposomal membrane composed of dipalmitoylphosphatidylcholine (DPPC) were investigated compared with those of soybean-derived sterol (SS) and cholesterol (Ch) using an electron spin resonance spectrometer. Three kinds of liposomes were prepared in the molar ratio of DPPC/X=7/4, where X is SS, Ch or SG. The fluidity close to the polar head groups increased with an increase of temperature in the DPPC membrane containing SS, Ch and SG in the range 35 to 45 degrees C. Those near the hydrophobic end changed with an increase in temperature in liposomes containing SS, Ch and SG, which had a fluidizing effect on the DPPC membrane below the transition temperature (Tm, 41.9 degrees C) and a condensing effect over the Tm. The fluidizing effects of these compounds around 37 degrees C near the polar head group and the hydrophobic end increased in the following order: Ch < SG < or = SS and SS < Ch < SG, respectively. SG increased the fluidity of liposomal membrane dramatically above the Tm (35.4 degrees C). These results suggest that the high fluidity close to the hydrophobic end of the liposomal membranes around 37 degrees C, the decrease of Tm, and the sigmoidal nature of fluidity vs. temperature are important factors in the effectiveness of liposomes containing SG as a carrier of drugs.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2000

Portal systemic encephalopathy presenting with dressing and constructional apraxia.

We report a case with portal systemic encephalopathy who presented with dressing and constructional apraxia and subtle weakness of the left hand. We initially suspected a cerebrovascular attack in the right cerebral hemisphere, but brain T1-weighted magnetic resonance (MR) imaging revealed high intensity in the basal ganglia and hyperammonemia was detected. We performed abdominal MR angiography, which visualized an intrahepatic portal systemic shunt. Cerebral blood flow, measured by xenon-enhanced computed tomography, was decreased in the bilateral, but more dominantly right-sided, parietal watershed regions. We speculate that these boundary territories might be susceptible to damage by toxic metabolites of hepatic encephalopathy.

Aged↗
PubMed2000

Restoration of prehension with the double free muscle technique following complete avulsion of the brachial plexus. Indications and long-term results.

BACKGROUND: Recent interest in reconstruction of the upper limb following brachial plexus injuries has focused on the restoration of prehension following complete avulsion of the brachial plexus. METHODS: Double free muscle transfer was performed in patients who had complete avulsion of the brachial plexus. After initial exploration of the brachial plexus and (if possible) repair of the fifth cervical nerve root, the first free muscle, used to restore elbow flexion and finger extension, is transferred and reinnervated by the spinal accessory nerve. The second free muscle, transferred to restore finger flexion, is reinnervated by the fifth and sixth intercostal nerves. The motor branch of the triceps brachii is reinnervated by the third and fourth intercostal nerves to restore elbow extension. Hand sensibility is restored by suturing of the sensory rami of the intercostal nerves to the median nerve or the ulnar nerve component of the medial cord. Secondary reconstructive procedures, such as arthrodesis of the carpometacarpal joint of the thumb, shoulder arthrodesis, and tenolysis of the transferred muscle and the distal tendons, may be required to improve the functional outcome. RESULTS: The early results were evaluated in thirty-two patients who had had reconstruction with use of the double free muscle procedure. Twenty-six of these patients were followed for at least twenty-four months (mean duration, thirty-nine months) after the second free muscle transfer, and they were assessed with regard to the long-term outcome as well. Satisfactory (excellent or good) elbow flexion was restored in twenty-five (96 percent) of the twenty-six patients and satisfactory prehension (more than 30 degrees of total active motion of the fingers), in seventeen (65 percent). Fourteen patients (54 percent) could position the hand in space, negating simultaneous flexion of the elbow, while moving the fingers at least 30 degrees and could use the reconstructed hand for activities requiring the use of two hands, such as holding a bottle while opening a cap and lifting a heavy object. The results were analyzed to identify factors affecting the outcome. CONCLUSIONS: The double free muscle procedure can provide reliable and useful prehensile function for patients with complete avulsion of the brachial plexus.

Accessory Nerve↗
PubMed1999

Limb allotransplantation in rats: combined immunosuppression by FK-506 and 15-deoxyspergualin.

The immunosuppressive effect of combined therapy using FK-506 and 15-deoxyspergualin was investigated in rat limb allotransplantation. The right hindlimb of an inbred Dark Agouti rat (RT1a) was transplanted to a Lewis rat (RT1l) and observed for 120 days. Eighty-eight transplantations were performed. Rejection of the grafts was evaluated histologically as well as macroscopically. A pathologic grading system was used to rate the severity of rejection. Limb survival time in Lewis rats receiving FK-506 therapy for days was significantly prolonged by combined therapy with 15-deoxyspergualin. Histologic study showed practically no rejection in all the graft-composing tissues except the skin and bone marrow, in which there was rejection. These results suggest that tissues like bone, cartilage, and muscle may survive transplantation with short-term combination FK-506 and 15-deoxyspergualin therapy even after withdrawal of both agents.

Animals↗
PubMed1999

The relationship between the rigidity of the liposomal membrane and the absorption of insulin after nasal administration of liposomes modified with an enhancer containing insulin in rabbits.

The relationship between the rigidity of the liposomal membrane and the absorption of insulin after nasal administration of liposomes modified with an enhancer containing insulin was investigated for the nasal delivery of peptide drugs in rabbits. The rigid liposomal membrane makes liposomes stable, protecting insulin from enzymatic degradation. Soybean-derived sterol (SS) or its sterylglucoside (SG) was used as an enhancer. Dipalmitoylphosphatidylcholine (DPPC) liposomes modified with SG had increased fluidity of the hydrophobic group of the liposome bilayer compared with the liposomes modified with cholesterol (Ch) or SS, as shown by measurements of the steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5,-hexatriene (DPH); however, the fluidity of the polar group of the liposome bilayer was decreased according to measurements of steady-state fluorescence anisotropy of dansylhexadecylamine (DSHA) at 37 degrees C. These findings suggest that the fluidity of the hydrophobic group of the liposome bilayer is responsible for the increase of liposomal leakage and instability of the liposomes. When insulin was administered nasally to rabbits as a solution, no hypoglycemic effect was observed. The administration of insulin contained in DPPC/SG (7/4, mole) liposomes with high fluidity caused a high glucose reduction of long duration (8 hr). DPPC/SS and DPPC/Ch (7/4) liposomes with low fluidity caused low glucose reductions. These results demonstrated that liposomes modified with SG can be useful as carriers of insulin administered nasally.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1999

[Comparison of epidemiological markers for Vibrio parahaemolyticus isolated from food poisoning].

Vibrio parahaemolyticus food poisoning, is the most prevalent among bacterial food poisoning in Japan. Study of epidemiologic markers is important in an attempt to trace the source of contamination. The purpose of this study was to compare seven different typing methods (serotyping, plasmid profile, antibiogram, phage susceptibility. TDH production, tdh and trh gene and pulsed-field gel electrophoresis [PFGE]) for V. parahaemolyticus. Outbreaks of V. parahaemolyticus food poisoning which occurred during the 13 years from 1981 to 1993 numbered 43 including 481 cases in Nagano Prefecture. Serovar O4:K8 was the most prlevalent serovar isolated, serovar O2:K3, O4:K63 and O3:K5 followed. Forty one strains of V. parahaemolyticus were used in this study. All of the strains were isolated from 12 food poisoning cases at Nagano Prefectual Research Institute for Health and Pollution. Of the 41 strains, twenty two strains (O4:K8, O4:K63) were sensitive to both phi VP 253 and phi VP 143 phages, six strains (O3:K5) to phage phi VP 143. Thirteen strains (O3:K29, O4:K11, O4:K12 and O5:KUT) were insensitive to both phages. CBPC, CBPC.CEZ and CBPC.CEZ.KM.SM resistant strains was determined in 22 strains out of 41 strains. Five strains of V. parahaemolyticus carried plasmid. Of the 41 strains, thirty nine strains were possessive to tdh gene and productive to TDH. Chromosomal DNA of the isolates from 12 different outbreaks was analysed by PFGE after Not I digestion. PFGE analysis of the digested DNA yielded 11 to 21 DNA fragments. Twelve distinctive fragment patterns were identified in 41 V. parahaemolyticus isolates from 12 different food poisonings. These results showed that the PFGE method is an useful tool to analyse an epidemiological survey for isolates of Vibrio parahaemolyticus food poisoning.

Electrophoresis, Gel, Pulsed-Field↗
PubMed1999

Double muscle transfer for upper extremity reconstruction following complete avulsion of the brachial plexus.

Recent interest in reconstruction of the upper limb following brachial plexus injuries has focused on the restoration of prehension following complete avulsion of the brachial plexus. The authors use free muscle transfers for reconstruction of the upper limb to resolve the difficult problems in complete avulsion of the brachial plexus. This article describes the authors' updated technique--the double free muscle procedure. Reconstruction of prehension to achieve independent voluntary finger and elbow flexion and extension by the use of double free muscle and multiple nerve transfers following complete avulsion of the brachial plexus (nerve roots C5 to T1) is presented. The procedure involves transferring the first free muscle, neurotized by the spinal accessory nerve for elbow flexion and finger extension, a second free muscle transfer reinnervated by the fifth and sixth intercostal nerves for finger flexion, and neurotization of the triceps brachii via its motor nerve by the third and fourth intercostal motor nerves to extend and stabilize the elbow. Restoration of hand sensibility is obtained via the suturing of sensory rami from the intercostal nerves to the median nerve. Secondary reconstruction, including arthrodesis of the carpometacarpal joint of the thumb and glenohumeral joint, and tenolysis of the transferred muscle and distal tendons, improve the functional outcome. Based on the long-term result, selection of the patient, donor muscle, and donor motor nerve were indicated. Most patients were able to achieve prehensile functions such as holding a can and lifting a heavy box. This double free muscle transfer has provided prehension for patients with complete avulsion of the brachial plexus and has given them new hope to be able to use their otherwise useless limbs.

Adult↗
PubMed1998

Estrogen protects against while testosterone exacerbates vulnerability of the lateral striatal artery to chemical hypoxia by 3-nitropropionic acid.

Gender differences in the vulnerability of the lateral striatal artery (1STR artery) to systemic intoxication with 3-nitropropionic acid (3-NPA, succinate dehydrogenase inhibitor) were studied. Subcutaneous injection of 3-NPA (20 mg/kg once a day for 2 days) induced striatal selective lesions in half of male rats associated with motor symptoms (rolling, paddling, recumbency, etc) while female rats were resistant. Lesions were located in the lateral striata and characterized by astroglial necrotic cell death, enhanced immunoreaction to factor VIII-related antigen, edema, extravasation of IgG and sometimes bleeding. The motor and histological disturbances were highly sex-dependent and modulated by changes in hormonal levels. Males were more susceptible than females. Castration had little effect but ovariectomy enhanced the vulnerability. Replacement therapy with testosterone increased while estradiol or tamoxifen suppressed the vulnerability in ovariectomized females. Investigation of the arterial architecture of the brain often revealed rectangular and acute angled branchings in the centrolateral striatum where the ISTR artery feeds. A parallel in vitro toxicity study demonstrated that an extreme Ca++ overload and a strong cellular swelling resulted in astrocytic cell death. Data suggest that 1STR artery and astrocytes are highly vulnerable to 3-NPA intoxication in males. The greater vulnerability of the ISTR artery may contribute to the pathogenesis of neurodegenerative diseases, striatal bleeding, etc. Protective effects of estrogen and tamoxifen may mediate gender differences often observed in these disorders and suggest their potential use as therapeutic agents for these disorders.

Animals↗
PubMed1998

Simultaneous optical imaging of intracellular Cl- in neurons in different layers of rat neocortical slices: advantages and limitations.

Simultaneous recording of changes in intracellular Cl- concentration ([Cl-]i) in individual neurons situated in different layers (e.g. II/III-VI) of neocortical slices was found to be feasible by means of optical fluorescence measurements using 6-methoxy-N-ethylquinolinium iodide (MEQ). Gamma-aminobutyric acid (GABA) caused a measurable increase in [Cl-]i in adult neocortical neurons, but a decrease in immature neurons. Developmental changes in the function of the Cl- pump and cation-Cl- co-transporters were evaluated using inhibitors such as furosemide (FURO), ethacrynic acid (ETA), and bumetanide (BMT). However, it was found that these inhibitors absorb and/or emit light of the wavelength that is used for the optical imaging of MEQ. In addition, quenching of MEQ fluorescence by Cl- and leakage of loaded MEQ was significantly enhanced at a higher temperature, which will limit experimentation at > 30 degrees C. Estimation of [Cl-]i in individual neurons in slices was made possible by calibrating intracellular MEQ fluorescence signals at known Cl- concentrations ([Cl-]) in the presence of tributyltin, a Cl(-)-OH- antiporter, nigericin, a K+-H+ antiporter, and KSCN. This enables comparison of [Cl-]i between neurons in different slices. Thus, optical imaging of [Cl-]i in brain slices can provide valuable spatial information about [Cl-]i dynamics and homeostasis, although it should be emphasized that the technique does have some limitations.

Animals↗
PubMed1998

A new immunosuppressant, FTY720, prolongs limb allograft survival in rats.

A new immunosuppressant, FTY720, was applied to limb allotransplants and its effectiveness was investigated. Using inbred rats, for which the major histocompatibility complexes were completely mismatched, 31 limb transplantations were performed and FTY720 was administered at a dose of 1.5 or 3 mg per kilogram per day for 10 days postoperatively. Rejection was monitored by the appearance of the skin of the grafted hind limb, soft radiograph, microangiography, and histology. In animals receiving no immunosuppressive therapy, the mean onset of rejection was 4.2+/-1.0 days postoperatively, and the grafted limbs became acutely necrotic. The mean onset of rejection was 6.0+/-0.9 days in animals receiving FTY720 at a dose of 1.5 mg per kilogram per day and 7.9+/-1.5 days in animals receiving FTY720 at a dose of 3 mg per kilogram per day. Survival of the grafted limbs was significantly prolonged compared with that in animals without immunosuppression. The immunosuppressive effect of FTY720 appeared to be dose dependent; however, complete suppression of rejection could not be obtained with FTY720 therapy alone.

Animals↗
PubMed1998

Treatment of chronic regional pain syndrome using manipulation therapy and regional anesthesia.

In a 4-year period, 17 consecutive patients with posttraumatic chronic regional pain syndrome were treated with a new technique, Movelat manipulation therapy. At average follow-up of 8 months, satisfactory results were achieved in 15 patients (88%), but 2 patients, 1 with digital nerve injury and 1 with ulnar nerve injury, did not respond to the therapy. Factors associated with good clinical response include chronic regional pain syndrome type I, i.e., dystrophy produced by a trauma to the hand but not involving a specific nerve injury, early-stage disease (within 3 months after trauma), and involvement of the upper limbs. Complications were rare and mild (pain over the tourniquet site in 3%, temporary dizziness in 1%). This therapy is simple and safe and recommended for early treatment of chronic regional pain syndrome.

Adult↗
PubMed1998

Revascularized intercalary bone allografts with short-term immunosuppression with cyclosporine in the canine.

To study the healing process of vascularized intercalary bone allograft after withdrawal of immunosuppressive drugs, allotransplantation of the tibia diaphysis with a vascular pedicle was performed in eight adult mongrel dogs (group 2) and assessments were made both during administration and after discontinuation of cyclosporin A. As controls, similar grafts with the vascular pedicles were removed and reimplanted back to the same animals (five dogs, group 1). Allotransplantation of frozen stored bone without a vascular pedicle (10 dogs, groups 3A and 3B) were also compared. No union occurred in most cases of frozen stored bone allotransplant because the transplanted bone was resorbed, leading to loosening and subsequent failure of osteosynthesis with the plate and screws used. Under cyclosporin A immunosuppression, bony union (i.e., when trabeculae were seen crossing the graft-recipient junction with obliteration of the junction line) occurred at almost similar time intervals in all dogs of group 2 (bone allotransplant with a vascular pedicle) by 3 months postoperatively, which was similar to those of group 1. No systemic side effects of cyclosporin A were observed. Cyclosporin A was discontinued 3 months following graft implantation. The bone graft became avascular within a week following withdrawal of cyclosporin A. However, bone union was maintained, and the transplanted bone never showed bone resorption, sclerosis, or fracture on serial radiographs up to the time the animals were sacrificed, between 5 and 14 months later. Histology at sacrifice showed that the transplanted allografts were being replaced at both ends by fresh bone derived from the transplantation bed. We conclude on the basis of the results of this study that solid bony union can be obtained in allotransplanted bone with a vascular pedicle if cyclosporin A is given for a brief period. After cyclosporin A is withdrawn, although the bone becomes nonviable secondary to rejection occurring in the blood vessels, its skeletal structure remains intact, enabling it to maintain its structural support while awaiting replacement by bony ingrowth from both ends of the graft.

Animals↗
PubMed1998

NMDA receptor-mediated differential laminar susceptibility to the intracellular Ca2+ accumulation induced by oxygen-glucose deprivation in rat neocortical slices.

Slices of somatosensory cortex taken from immature rats on postnatal day (P)7-14 were labeled with fura-2. Intracellular Ca2+ concentration ([Ca2+]i) was monitored in identified pyramidal cells as the ratio of fluorescence intensities (RF340/F380) during oxygen-glucose deprivation. The RF340/F380 ([Ca2+]i) of individual pyramidal cells was monitored in each of the cortical layers II-VI simultaneously. Neurons in all neocortical layers exhibited significant increases in [Ca2+]i that varied with the duration of oxygen-glucose deprivation. Individual neurons responded to oxygen-glucose deprivation with abrupt increases in [Ca2+]i after various latencies. The ceiling level of the [Ca2+]i increase differed from cell to cell. Neurons in layer II/III showed significantly greater increases in [Ca2+]i than those in layers IV, V, or VI. Kynurenic acid, a nonselective glutamate receptor antagonist, and bicuculline, a selective gamma-aminobutyric acid (GABA)A receptor antagonist, suppressed the intracellular Ca2+ accumulation induced by oxygen-glucose deprivation in all neocortical layers examined. After kynurenic acid, but not after bicuculline, there was no longer a differential [Ca2+]i increases in layer II/III. Both 2-amino-5-phosphonopentanoic acid (AP5), a selective N-methyl-D-aspartate (NMDA) receptor antagonist, and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a non-NMDA receptor antagonist, strongly suppressed the intracellular Ca2+ accumulation induced by oxygen-glucose deprivation in all layers. The laminar difference in terms of the [Ca2+]i increases was abolished by AP5, but not by CNQX. These results indicate that layer II/III cells are the most prone to oxygen-glucose deprivation-induced intracellular Ca2+ accumulation, and that this is primarily mediated by NMDA receptors. Thus, layer II/III neurons would be more likely to suffer cellular Ca2+ overload and excitotoxicity during ischemia than layer IV-VI cells. Such a differential laminar vulnerability might play an important role in determining the pathological characteristics of the immature cortex and its sequelae later in life.

2-Amino-5-phosphonovalerate↗
PubMed1998

Changes in intracellular Ca2+ induced by GABAA receptor activation and reduction in Cl- gradient in neonatal rat neocortex.

We have studied the effects of gamma-aminobutyric acid (GABA) and of reducing the Cl- gradient on the [Ca2+]i in pyramidal neurons of rat somatosensory cortex. The Cl- gradient was reduced either with furosemide or by oxygen-glucose deprivation. Immature slices taken at postnatal day (P)7-14 were labeled with fura-2, and [Ca2+]i was monitored in identified pyramidal cells in layer II/III as the ratio of fluorescence intensities (RF340/F380). The magnitude of the [Ca2+]i increases induced by oxygen-glucose deprivation was significantly reduced (by 44%) by bicuculline (10 microM), a GABAA receptor antagonist. Under normal conditions, GABA generally did not raise [Ca2+]i, although in some neurons a small and transient [Ca2+]i increase was observed. These transient [Ca2+]i increases were blocked by Ni2+ (1 mM), a blocker of voltage-dependent Ca2+ channels (VDCCs). Continuous perfusion with GABA did not cause a sustained elevation of [Ca2+]i but bicuculline caused [Ca2+]i oscillations. After inhibition of Cl- extrusion with furosemide (1.5 mM), GABA induced a large [Ca2+]i increase consisting of an initial peak followed by a sustained phase. Both the initial and the sustained phases were eliminated by bicuculline (10 microM). The initial but not the sustained phase was abolished by Ni2+. In the presence of Ni2+, the remaining sustained response was inhibited by the addition of 2-amino-5-phosphonopentanoic acid (AP5, 20 microM), a selective N-methyl-D-aspartate (NMDA) receptor antagonist. Thus the initial peak and the sustained phase of the GABA-evoked [Ca2+]i increase were mediated by Ca2+ influx through VDCCs and NMDA receptor channels, respectively, and both phases were initiated via the GABAA receptor. These results indicate that, in neocortical pyramidal neurons, a reduction in the Cl- gradient converts the GABAA receptor-mediated action from nothing or virtually nothing to a large and sustained accumulation of cellular Ca2+. This accumulation is the result of Ca2+ influx mainly through the NMDA receptor channel. Thus GABA, normally an inhibitory transmitter, may play an aggravating role in excitotoxicity if a shift in the Cl- equilibrium potential occurs, as reported previously, during cerebral ischemia.

2-Amino-5-phosphonovalerate↗
PubMed1998

Fluorometric measurement of intracellular pH in vivo in feline cerebral cortex during ischemia and reperfusion.

Intracellular acidosis has been considered to play an pivotal role in the progression of neuronal damage after cerebral ischemia. However, continuous measurement of the intracellular potential of hydrogen (pH) has not been done during and after ischemia. We measured temporal changes in intracellular pH in the feline cerebral cortex in vivo during and after ischemia using a novel fluorescent pH probe, 2',7'-biscarboxyethyl carboxyfluorescein (BCECF). A closed cranial window was installed in the left temporal skull. BCECF acetoxymethyl ester was superfused over the cortex, hydrolyzed and trapped in cortical cells. Intracellular pH was measured utilizing excitation light at 507 nm and fluorescent light at 550.5 nm. Focal cerebral ischemia for 60 minutes was induced by means of middle cerebral artery occlusion. Intracellular pH in the severely ischemic group became significantly acidic (p < 0.01) during ischemia and the acidosis persisted for at least 30 minutes after recirculation. The pH change was not significant in the mildly ischemic group. The severity of ischemia was determined based on the mean transit time, which was calculated from the hemodilution curve obtained by bolus injection of saline. The extent of ischemia was further confirmed pathologically (p < 0.01). The above results suggest that intracellular acidosis resulting from severe ischemia persists even after recirculation.

Animals↗
PubMed1997

Importance of interferon-gamma in protective immunity against Hymenolepis nana cysticercoids derived from challenge infection with eggs in BALB/c mice.

The function of cytokines produced during Hymenolepis nana egg infection in mice in protective immunity against re-infection was examined. Treatment of mice with monoclonal antibody (MAb) against mouse interferon (IFN)-gamma caused suppression of protective immunity against H. nana re-infection when the MAb was injected intraperitoneally at a daily dose of 40.0 mg kg-1 during the effector phase of protective immunity. Although high levels of IFN-gamma, tumor necrosis factor (TNF)-alpha and interleukin (IL)-1 beta were released into the intestinal tracts of the parasitised mice at challenge infection, there was almost no release of these cytokines in mice treated with the MAb. Daily administration of rolipram failed to suppress the protective immunity, even when 400 micrograms kg-1 of the agent was administered into mice during the effector phase of immunity. Treatment of mice with rolipram completely suppressed both TNF-alpha and IL-1 beta production in intestinal tracts, induced by H. nana challenge infection. However, endogenous IFN-gamma production in the intestine was scarcely affected by rolipram. These results strongly suggest that IFN-gamma is the most important (or essential) cytokine in protective immunity to H. nana re-infection, rather than TNF-alpha and IL-1 beta.

Animals↗